Advanced polymer matrix composites have become established high-performance structural materials that enjoy a rapidly expanding range of aerospace applications. The major driving force for the use of these composites is the reduced weight brought about by high stiffness/weight and high strength/weight ratios. Added to this is the potential for significantly lower component cost.
For example, polyimides as matrices offer an unparalleled versatility compared to most other organic matrices. They can be prepared using a variety of starting materials and synthetic methods tailor-made to specific applications. By the appropriate choice of starting materials we can produce desirable variations in glass transition temperature, oxidative stability, toughness, and adhesion. Outstanding thermal stability and relative ease of fabrication have established polyimides as viable matrix materials.
Unfortunately, a factor strongly limiting the commercial applicability of these types of composites is their toughness, or their ability to withstand incidental impacts. The same elevated T.sub.g that makes these materials suitable as high temperature polymer matrices produces an enhanced susceptibility to bird impact, dropped tooling, etc.
Toughness in polyimides is usually addressed by the incorporation of more flexible linkages into the thermoset structure. Unfortunately, along with the additional cost and reduction in thermal capability these methods have so far produced only limited improvements in toughness.
Accordingly, it is an object of the present invention to provide for the toughening of polymeric matrices, such as thermosetting polyimide matrices, using nanoporous particulate reinforcement.
It is also an object of the present invention to improve the effects of particulate reinforcement on overall mechanical properties, such as flexural, impact, and compression strengths.
Further, it is an object of the present invention to integrate successful matrix processing into fiber-reinforced composite manufacturing. The main objective will be to ensure that the presence of small amounts of reinforcing particulates do not compromise the efficiency of the composite formation process.